1995 Volume 74 Issue 3 Pages 173-178
Thermodynamic analyses were done for better understanding of the structural changes in iron based coal liquefaction catalysts during sulfidation and oxida-tion. Chemical potential diagrams were used to evaluate the stability/reactivity of several iron phases such as Fe, Fe3O4 (magnetite), Fe2O3 (hematite), Fe0.877S (Pyrrhotite), FeS2 (phyrite), FeSO4, and Fe2 (SO4) 3. These analyses indicated that most of the iron starting materials would be converted into thermodynamically stable phase Fe0.877S under typical coal liquefaction conditions, i.e., reaction temperature of 698K under reducing/sulfiding conditions. However, the sulfidation paths were quite different in Fe2O3 and FeSO4 as the starting materials, and were influenced significantly by the sul-fidation conditions, such as temperature, P (H2S) /P (H2) and P (H2O). These analyses suggested that steaming conditions would facilitate the sulfidation, but cause the gas phase transport of hydrated compounds, which might be one of the reasons for catalyst agglomeration.